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cannabis information leaflet

Date published: 2019-06-14

Organization: Health Canada

Common immediate effects of THC

some effects could last as long as 24 hours

Everyone’s response to cannabis differs and can vary from one time to the next. To minimize your risk or if you are a new consumer, look for a product containing 2.5 mg of THC or less or 10% THC (100 mg/g) or less, and an equal or higher amount of CBD.

Talk to your health care practitioner if you have any questions or concerns regarding cannabis use and your health.

It’s likely most of these products – even those called “CBD oils” – will be illegal to possess or supply. There’s a good chance they will contain THC, and may not be safe to use.

A prescription for medical cannabis would only be given when it was believed to be in your best interests, and when other treatments had not worked or were not suitable.

Long-term pain

Many people having chemotherapy will have periods where they feel sick or vomit.

Health stores sell certain types of “pure CBD”. However, there’s no guarantee these products will be of good quality.

Currently, it is only likely to be prescribed for the following conditions:

According to Home Office Statistics on drug use in the UK from 2016, cannabis continues to be the most commonly used illegal drug, with 6.5% of adults aged 16-59 years having used it in the preceding year (around 2.1 million people) – similar to 2014/15 but statistically significantly lower than a decade ago (8.7%) [2] . Among younger adults aged 16-24 years, cannabis was also the most commonly used drug, with 15.8% having used it in the preceding year (around 975,000 young adults) [1] .

Symptoms of schizophrenia may be worsened.


Cannabis induces a relaxed state characterised by a series of disconnected thoughts. There may also be:

Treatment of almost all medical conditions has been affected by the COVID-19 pandemic. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Please visit to see if there is temporary guidance issued by NICE in relation to the management of this condition, which may vary from the information given below.

Sibbald B ; Conditional okay for cannabis prescription drug. CMAJ. 2005 Jun 21172(13):1672.